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# Calibration Calibration Calibration Challenge 1 • by mikesanye

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```									Calibration
Calibration Challenge #1
• A label may call for 1 pint of pesticide to be
applied over an entire acre (1 pint per acre).
• An acre is 43,560 ft2. (208 ¾ ft x 208 ¾ ft)
• Some labels call for as little as ½ or 1/10 of an
ounce of dry material (WPs) per acre.

• How can this be done?
Dilution is the Solution
• Its easier to spread 20 gallons of water (with
1 pint added) over 1 acre than it is to spread
1 pint by itself.
• The goal…….
– Find out how many gallons it takes your
sprayer to cover one acre
Calibration Dilemma #2
How much pesticide do I add to the
tank?
• You will need to know:
– How many gallons it takes your sprayer to
cover one acre…..Gallons per acre or GPA ?
– How many acres you can spray with a
certain volume?
– What is the labeled rate of the pesticide?
– Make the dose calculation (how much do I
add to the tank)
Calibration Tip
• Keep everything constant.
• When you are field spraying, use the same
speed, sprayer pressure and nozzle type as
you did when you calibrated.
• Keep a calibration log.
Checking your Field Speed
• Set out a 200 foot course.
• Drive the course at a comfortable and
practical field speed.
• Use this formula to double check your
speed
• MPH = 136.4          Ex: 136.4 = 5 MPH
Time*                27 sec.
* Time = seconds it took to drive the course
Determining GPA
3 methods
• Calibration Strip Method
– Preferred
– Most accurate
• 5940 Method
• 128th acre method
But first….
Determining GPA
with a backpack or hand sprayer
18 ½ feet

Measure out an 18 ½ by     1
18 ½ foot square in an     8
area similar to what you   ½
will spray                 feet
Backpack - GPA
1.     18 ½ x 18 ½ foot square
2.     Spray & time yourself
3.     Spray into bucket for same time and using same
pressure.
4.     Collect in Ounces
5.     Ounces = GPA
6.     Why does this work?

•        18 ½ x 18 ½ feet = 342 ft2 which is 128th of an acre
•        There are 128 ounces in a gallon
Backpack GPA
Example
• Sprayed calibration square and it took 45
seconds
• Sprayed into bucket for 45 seconds and
collected 64 ounces
• GPA = 64
Calibration Strip Method
• Take a small area and relate it to an acre
• Need to know area of calibration test
strip (in acres). One acre = 43,560 ft2
• Amount of liquid sprayed over strip
• Remember:
G---gallons applied per strip
P divided by
A ---acres in test strip
=   GALLONS PER ACRE
Calibration Strip Method
Example:
• Calibration strip is 66 feet x 66 feet or
4,356 ft2  43,560 ft2 = 0.10 acres
• 3 gallons applied per strip
• 3 gal/strip  0.10 acres = 30 GPA
Boom Sprayers
• No matter what method of
calibration is used, you
need to….
– check nozzle spacing
– check output across the boom.
Checking Nozzle Spacing & Height
Nozzle Orientation
Nozzle output
Checking Nozzle Output
Remember!
Check Nozzle Spacing

20”

Then……
Check Nozzle Output For a Given
Amount of Time! (usually 1 minute)
Nozzle 1            Nozzle 2           Nozzle 3
51 oz               50 oz              42 oz

•Nozzle 1 = 51 oz
•Nozzle 2 = 50 oz
•Nozzle 3 = 42 oz
143 oz ÷ 3 = 48 oz. (average)
Checking Nozzle Output

• The average of all the nozzles is 48 oz.
• This is the benchmark you use to determine
which nozzles need to be replaced or
cleaned.
• A 5% error on either side of the average is
commonly used.
Calibration Tip
• To find 5%
– Find your average… 48 oz
– Move the decimal place one space to the left.
48. = 4.8   This is a 10% error

–   Divide by 2 = 2.4. This is 5% error
–   Now add 2.4 to 48 for +5%
–   Subtract 2.4 from 48 for – 5%
–   Error range = 45.6          50.4
–   Any nozzle output between 45.6 and 50.4 is OK!
Boom Sprayer
Calibration Strip Method
• Need swath width (W) x Course length (L)
• Gives you sq. ft (ft2) of the test strip
• Find acreage of the test strip
(test strip ft2 43,560 ft2)
• Find liquid applied per strip (gallons)
• Use simple math

Gallons applied per strip   =   GPA
Test strip in Acres

Keep going for example
Using test strip
Collect from each nozzle using
test strip time.

Or you can refill the sprayer and note how many gallons it took
Figure your GPA
• Example:
–   Swath width is 35 ft
–   Course length is 200 ft
–   Calibration strip = 7,000 ft2 (35 x 200)
–   Test strip is 0.16 acres (7000 ÷ 43560)
–   You collect from all the nozzles or refill the tank
• 4 gallons is collected
– 4 gallons ÷ 0.16 acres = 25 acres
Broadjet

0.5 g
100   3400 = 0.078 acres
in 13 sec.
43560

34

0.5 g 0.078 acres = 6.4 GPA
5940 Method
• Based on nozzle output within 5% of the
average.
• Not only gives you GPA but also how much you
need to collect from under each nozzle to reach
a desired GPA.
• Uses the following basic formula:
GPA = GPM X 5940
MPH X W
• GPA = Gallons Per Acre
• GPM = Gallons per Minute collected from a single
nozzle (Make sure all nozzle are within a
5% range.)
• 5940 is a constant
• MPH = Field Speed
• W = 1) width between nozzles or
2) width of a broadjet swath in inches.
5940 Example
• You have checked all your nozzles and the average is 64
ounces per minute (OPM). All nozzles are within 5% of
this average.
• 64 OPM = 0.5 GPM (64 ounces ÷ 128 oz./gallon)
• Your field speed is 5 MPH
• Your nozzles are spaced 20” apart

GPA = GPM X 5940 = 0.5 GPM x 5940 = 2970
MPH X W        5 MPH x 20    100
GPA = 29.70 or 30 GPA
Using 5940 to find out how much you
need to collect to get a certain GPA!
• Rearrange the basic formula to look like
this:
GPM = GPA x MPH x W
5940
5940 Example #2
• You want to apply 20 GPA.Your broadjet has a
swath of 35 feet. Your field speed is 5 MPH
GPM =    GPA x MPH x W
5940
GPM =    20 GPA x 5 MPH x 420 (35 ft x 12”)
5940
7 GPM = 42,000
5940
You need to collect 7 GPM to get 20 GPA
Boom Sprayer GPA
128th Acre Method
•   Measure distance between nozzles.
•   Use chart for test course distance.
•   Nozzle output must be close to uniform
•   Ounces collected from one nozzle = GPA

Nozzle spacing (in.) Test Strip (ft)
20                 204 *         *340 ÷ spacing (ft)
30                 136
36                 113
38                 107
40                 102
Broadjet -= 128th Acre Method
• Measure swath width
• Set calibration course
Swath width       Course length
35                 156 *    *5460 ÷ W (ft)
40                 136
45                 121
• Time yourself
• Collect for same time
• Pints collected = GPA
Boom Output and GPA

Using the 128th method you get:
15 ounces = 15 GPA
Check the label
May be too low.
How many acres can you
spray.

Volume used   = Acres
GPA
How many acres can you spray - Example

• Have a 1000 gallon tank. Only want to apply 500
gallons.
• GPA = 25
•     500 gallons = 20 acres
25 GPA
• Backpack
5 gallons = 0.078 acres
64 GPA
Acres - Example 2
• Suppose you only want to spray 10 acres.
• GPA = 25 (25 GPA)
• Now just back-multiply….
Gallons??? = 10 acres
25 GPA
• 25 GPA x 10 acres = 250 gallons of total
mix is needed (pesticide and water)
Dosage Determination
• Listed rate per acre
…Read the label
• Lbs. of a.i. per acre
– Liquid
– % W.P.
Listed Rate Per Acre
• Acres x labeled rate = dose
• 10 acres x 1 pint/acre = 10 pints in a given
volume
–      300 gallon mix = 10 acres
30 GPA
– 10 acres x 1 pint/acre = 10 pints
– 10 pints of product to make a 300 gallon mix.
Pounds per Acre - Liquid
Example – 1 lb of a.i. is recommended per acre

1 gal. Formulation x 1 lb a.i = 0.5 x 1 = 0.5 gal formulation/acre
2 lb a.i.     Acre

Rate        =    1       = 0.5 gallons formulation/acre
Lbs. a.i./gallon      2
Dry Formulations
• 2 lbs per acre of an 80% WP is prescribed
1 lb formulation x   2 lb a.i.   =   2.5 lbs formulation/acre
0.80 lb a.i.      Acre

Rate per acre =   2 lb a.i.   = 2.5 lbs
% a.i.          0.80
How much product to add to
tank.
• Rate/acres x acres treated

• Example:

1 pt/acre x 10 acres = 10 pints.

• Backpack
0.078 acres x 16 oz. = 1.2 oz.

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